Disk cartridge which accommodates an information-recording disk

ABSTRACT

A disk cartridge, which is compact, which requires a small number of parts, and which is easily assembled, is provided. The disk cartridge of the present invention comprises an upper case and a lower case. Each of the upper case and the lower case is formed to be substantially circular. The upper case and the lower case define a disk-accommodating section when the lower case and the lower case overlap with each other. The disk cartridge is opened/closed by rotating the upper case relative to the lower case about a base point of a movable section which is provided for the upper case and/or the lower case. An information-recording disk is accommodated and removed in a state in which the disk cartridge is open. The disk cartridge further comprises an engaging section for engaging the upper case and the lower case with each other and an opening for exposing a central portion and an information-recording surface of the information-recording disk, the opening being formed at least on surfaces of the upper case and the lower case.

CROSS-REFERENCE TO RELATED APPLICATION

This application is Continuation of U.S. patent application Ser. No.10/617,209, filed on Jul. 11, 2003 now U.S. Pat. No. 6,948,180, thedisclosure which is incorporated herein by reference in its entirety.

BACKGROUND

The present invention relates to a disk cartridge for accommodating adisk-shaped information-recording medium such as DVD and MO. Inparticular, the present invention relates to a disk cartridge which iscompact and which makes it easy to insert and remove a disk.

As shown in FIG. 7, a disk cartridge 200, which has been hitherto usedfor the information-recording medium such as DVD, comprises a diskholder 101 for holding a disk 102 and a cartridge case 100 foraccommodating the disk holder 101. The cartridge case 100 is a casehaving a thin thickness with a substantially square surface, and it isprincipally composed of an upper case and a lower case. Each of theupper case and the lower case is a formed product made of syntheticresin. An internal space is formed by overlapping the upper case and thelower case with each other. An opening 106 is provided on one of sidesurfaces of the cartridge case 100. The disk holder 101, which holds thedisk 102, is inserted in the direction of the arrow AR7 from the opening106, and thus the disk 102 is accommodated in the disk cartridge 200. Anopening 103 is provided on one of the surfaces of the cartridge case 100(for example, on the upper case). Further, a slidable shutter 104 isprovided to cover the opening 103. When the disk cartridge, whichaccommodates the disk 102, is inserted into aninformation-recording/reproducing apparatus, a predetermined portion ofthe information-recording/reproducing apparatus allows the shutter 104to slide in the direction perpendicular to AR7 to open the opening 103so that an information-recording/reproducing surface of the disk 102accommodated in the disk cartridge 200 is exposed. Accordingly, arecording and reproducing head of the information-recording/reproducingapparatus is accessible with respect to the information-recordingsurface of the disk 102.

However, the disk cartridge having the structure as shown in FIG. 7 hasan area which is about 1.6 times the area of the circular plate-shapeddisk. The useless space has been consumed in theinformation-recording/reproducing apparatus in order to accommodate thedisk cartridge. The useless space has been one of the factors toobstruct the miniaturization and lower the degree of freedom of thedesign of the information-recording/reproducing apparatus itself.Further, the conventional disk cartridge has involved such problems thatthe structure is complicated and the number of parts is increased,because the disk is held by the disk holder. Due to such problems, theproduction cost of the disk cartridge has been expensive, and it hasbeen inconvenient to accommodate or remove the disk.

SUMMARY

Thus, an object of the present invention is to provide a disk cartridgewhich is compact, which requires a small number of parts, and which iseasily assembled.

According to a first aspect of the present invention, there is provideda disk cartridge which accommodates an information-recording disk, thedisk cartridge comprising:

an upper case which has a first engaging section;

a lower case which has a second engaging section engageable with thefirst engaging section and which defines a disk-accommodating sectionwhen the lower case overlaps with the upper case; and

a movable section which is provided for the upper case and/or the lowercase and which rotates the upper case relative to the lower case,wherein:

each of the upper case and the lower case is formed to be substantiallycircular while having at least a pair of parallel flat sections disposedat opposing positions on an outer circumference; and

an opening is provided on at least one of surfaces of the upper case andthe lower case.

The disk cartridge of the present invention is constructed by the uppercase and the lower case. The upper case and the lower case are formed tobe substantially circular respectively. Therefore, the surface area ofthe disk cartridge is decreased, and it is possible to miniaturize thedisk cartridge. Accordingly, it is possible to reduce the dead space ofthe recording and reproducing apparatus for the information-recordingdisk. Further, at least the pair of parallel flat sections are formed atthe opposing positions on the outer circumference of the disk cartridge.The flat sections can be used as guides when the disk cartridge isinserted into the information-recording/reproducing apparatus. Further,the disk-accommodating section is defined by overlapping the upper caseand the lower case with each other. The disk cartridge is opened/closedby rotating the upper case relative to the lower case about the basepoint of the movable section which is provided for the upper case and/orthe lower case. The information-recording disk is accommodated andremoved in the state in which the disk cartridge is open. The diskcartridge of the present invention is provided with the first and secondengaging sections (for example, a fastening section and an elastic tabengageable therewith) in order to engage the upper case and the lowercase with each other. Accordingly, the closed state of the diskcartridge is maintained. The opening, which is formed to expose theinformation-recording surface and the central portion of theinformation-recording disk provided with a spindle hole, is provided onat least one surface of the upper case and the lower case. The spindle,which rotates the disk, is inserted through the opening, and therecording and reproducing head makes the access with respect to theinformation-recording surface of the disk.

It is desirable that at least one of the upper case and the lower casehas a plurality of ribs which surround the disk and which are formed bysubstantially concentric cylindrical surfaces, and the first engagingsection and the second engaging section are formed outside the ribs.Accordingly, for example, when the engaging section composed of anelastic member is used, it is possible to avoid any influence whichwould be otherwise exerted by the elastic deformation thereof on thedisk accommodated in the disk cartridge. The first engaging section andthe second engaging section are preferably provided on the same plane asan outer circumferential surface of the disk cartridge, or inside theouter circumferential surface. Accordingly, the disk cartridge isprevented from being caught by any part when it is inserted into theinformation-recording/reproducing apparatus, and thus it is possible tosmoothly insert and remove the disk cartridge.

In the disk cartridge of the present invention, it is desirable that thefirst engaging section and the second engaging section are provided on aside opposite to the movable section in relation to a center of the diskcartridge. Further, it is desirable that two pairs of first engagingsections and second engaging sections are provided. Further, it isdesirable that the two pairs of the first engaging sections and thesecond engaging sections are provided substantially symmetrical to aline which passes through the center of the disk cartridge and themovable section. Accordingly, it is possible to more reliably maintainthe state in which the disk cartridge is closed.

In the disk cartridge of the present invention, it is desirable that theopening is open so that an information-recording surface and a centralportion of the information-recording disk are exposed. Further, it isdesirable that the disk cartridge further comprises a bridge which isprovided at an end of each of the upper case and the lower case on aside on which the opening is formed. Accordingly, the disk cartridge isreinforced against the decrease in rigidity of the case which would beotherwise caused by the opening provided for each of the cases. Further,it is desirable that the bridge is formed to have a thickness which isthinner than a thickness of the disk cartridge. Accordingly, it ispossible to uniquely determine the direction in which the disk cartridgeis inserted into the information-recording/reproducing apparatus, and itis possible to prevent the disk cartridge from any erroneous insertion.

In the present invention, the upper case, the lower case, and themovable section may be formed by integrated formation. When the diskcartridge is manufactured by means of the integrated formation, then itis possible to further decrease the number of parts, and it is possibleto simplify the production and assembling steps.

According to a second aspect of the present invention, there is provideda disk cartridge which accommodates an information-recording disk andwhich is inserted into an information-recording/reproducing apparatus torecord and/or reproduce information, the disk cartridge comprising:

an upper case and a lower case each of which has an opening forinserting a spindle and a head of the information-recording/reproducingapparatus, the opening being formed over a region ranging from a centralportion of the disk cartridge to an end of the disk cartridge, wherein:

the upper case and the lower case are openable/closable by a hinge withengaging sections for maintaining a closed state being provided at leastat two positions on a side opposite to the hinge as viewed from a centerof the disk cartridge; and

end portions which are defined by the opening and which are disposed atan end of the disk cartridge are connected by a bridge.

The disk cartridge according to each of the aspects described above mayfurther include the information-recording disk accommodated therein. Thedisk cartridge of the present invention is provided singly as the diskcartridge or in a form in which the information-recording disk isaccommodated in the disk cartridge.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A shows top, bottom, front, back, right side, and left side viewsillustrating a disk cartridge according to an embodiment of the presentinvention. FIG. 1B shows a sectional view taken along a line A—A shownin FIG. 1A illustrating the disk cartridge. FIG. 1C shows a magnifiedview illustrating a portion A′ shown in FIG. 1B.

FIG. 2A shows top, bottom, front, back, and side views illustrating anupper case for constructing the disk cartridge shown in FIG. 1. FIG. 2Bshows a lower case for constructing the disk cartridge shown in FIG. 1.

FIGS. 3A and 3B show magnified views illustrating those disposed in thevicinity of an engaging section of the disk cartridge, and FIGS. 3C and3D show sectional views taken along lines B—B corresponding to FIGS. 3Aand 3B respectively.

FIGS. 4A and 4B show situations in which a disk is accommodated in thedisk cartridge according to the embodiment of the present invention.

FIGS. 5A, 5B and 5C show situations in which the disk is removed fromthe disk cartridge according to the embodiment of the present invention.FIG. 5B shows a magnified view illustrating a portion A″ shown in FIG.5A.

FIG. 6 is illustrative of the explanation in relation to the insertionof the disk cartridge according to the embodiment of the presentinvention into an information-recording/reproducing apparatus.

FIG. 7 shows a conventional disk cartridge for an information-recordingmedium.

DETAILED DESCRIPTION OF THE EMBODIMENTS

An embodiment of the present invention will be explained with referenceto the drawings. However, the present invention is not limited thereto.

Structure of Disk Cartridge

FIG. 1A shows top, bottom, front, back, right side, and left side viewsillustrating a disk cartridge 1 in a state in which a disk isaccommodated according to the present invention. The disk cartridge 1 isa circular plate-shaped case, and it is constructed by an upper case 2and a lower case 3. The disk 5 is accommodated in the space which isformed by overlapping and combining the upper case 2 and the lower case3. Each of the upper case 2 and the lower case 3 is composed of a formedproduct of synthetic resin, for example, polycarbonate, which issubstantially circular with a plurality of circular arcs having radii of40 to 55 mm. The upper case 2 and the lower case 3 are formed to haveshapes which are substantially identical with each other. Flat sections61, which are opposed to one another and which extend in parallel, areformed at outer circumferential portions of the upper case 2 and thelower case 3 respectively. For the convenience of explanation, a plane,which passes through the central position X of the cartridge 1 and whichis parallel to the flat sections 61, is defined as “central plane AX”.The disk 5 is an information-recording medium having an outer diameterof 80 mm, an inner diameter (diameter of spindle hole) of 15 mm, and athickness of 1.2 mm. An information-recording surface is formed in anarea of radii of 24 mm to 38 mm.

Next, an explanation will be made with reference to FIG. 2 about detailsof the upper case 2 and the lower case 3. As shown in FIG. 2A, the uppercase 2 has a recess (cutout) 25 which is formed at one end 22 in thecentral plane AX and which is indented in a rectangular form toward thecenter X of the upper case 2. Pins 25′a are formed to protrude onmutually opposing side walls 25′ which define the recess 25. As shown inFIG. 2B, the lower case 3 has a portion which is provided at one end 32in the central plane AX and which is formed to be flat over apredetermined length so as to be perpendicular to the central plane AX.A projection 35 is formed at the end 32 in a direction which is directedin the thickness direction (perpendicular to the plane of paper) of thelower case 3 and which is directed in the direction to make theengagement with the upper case 2. Holes 35′a, into which the pins 25′aof the upper case 2 are insertable, are formed on both side walls 35′ ofthe projection 35. When the pins 25′a are fitted into the holes 35′a,the pins 25′a and the holes 35′a form a hinge (movable section) 7 of thedisk cartridge 1 as shown in FIG. 1A. The disk cartridge 1 isopened/closed in accordance with the relative rotation of the upper case2 and the lower case 3 about the rotary shaft of the hinge 7.

As shown in FIGS. 1A and 2A–2B, openings 20, 30 are provided on thesurfaces of the upper case 2 and the lower case 3. Each of the openings20, 30 is composed of a semicircular portion which is formed about thecenter X of each of the cases, and a rectangular portion which extendsfrom the semicircular portion to arrive at the other end 24, 34 in thecentral plane AX. The disk 5, which is accommodated in the cartridge 1,has a spindle hole 51 and an information-recording surface 53 which areexposed through the openings 20, 30. Bridges 21, 31, each of whichextends in the circumferential direction, are formed at the other ends24, 34. The bridges 21, 31 compart the openings 20, 30, and theyreinforce the disk cartridge provided with the openings 20, 30 havingrelatively large areas so that the rigidity of the disk cartridge is notlowered.

As shown in FIGS. 1B and 1C, the bridges 21, 31 are formed so that thebridge 21 is arranged in an overlapped manner at the outside of thebridge 31 in the state in which the disk cartridge 1 is closed. That is,the bridge 21 and the bridge 31 are provided on the upper case 2 and thelower case 3 at such positions that the outer surface of the bridge 31is overlapped with the inner surface of the bridge 21. The inner surfaceand the outer surface are formed to have an identical angle ofinclination. Accordingly, the disk cartridge 1 can be opened/closedwithout causing any interference between the bridge 21 and the bridge31. As shown in FIGS. 2A–2B, the bridges 21, 31 are formed to be thinnerthan the thicknesses of the upper case 2 and the lower case 3respectively. As shown in FIG. 1A, flat sections 63, which extend in thedirection perpendicular to the central plane AX, are formed at thejoining portion between the bridge 21 and the upper case 2 and at thejoining portion between the bridge 31 and the lower case 3.

Next, an explanation will be made about an opening/closing mechanism ofthe disk cartridge 1 with reference to FIGS. 2A–2B and 3A–3B. As shownin FIG. 2A, fastening sections 23 are provided at two positions on theouter circumference of the upper case 2 in the vicinity of the bridge 21so that the fastening sections 23 are symmetrical in relation to theplane AX, that is, the fastening sections 23 are symmetrical to a linewhich passes through the center X of the disk cartridge 1 and a centerof the hinge 7. As shown in FIG. 2B, locking elastic tabs 33 areprovided at two positions on the outer circumference of the lower case 3in the vicinity of the bridge 31 so that the locking elastic tabs 33 aresymmetrical in relation to the plane AX. The locking elastic tabs 33 areformed at such positions that they are engaged with the fasteningsections 23 when the upper case 2 and the lower case 3 are overlappedwith each other by the aid of the hinge. When the engaging sections areprovided at the two positions, then the upper case 2 and the lower case3 are reliably fixed, and the disk cartridge is more effectivelyprevented from any erroneous opening which would be otherwise causedwhen any impact or shock is applied from the outside. It is enough thatthe engaging sections are formed on the same plane as the contoursurface of the disk cartridge 1, or the engaging sections are formedinside the contour surface.

As shown in FIGS. 3A–3D, the fastening section 23 is an arm like acantilever spring extending along the outer circumference of the uppercase 2. A hole 23′ is formed through the arm. The locking elastic tab 33is also an arm like a cantilever spring extending along the outercircumference of the lower case 3. A projection 33′, which is fitted tothe hole 23′, is formed at the tip of the arm. When the upper case 2 andthe lower case 3 are overlapped with each other by the aid of the hinge,i.e., in the state in which the disk cartridge 1 is closed, theprojection 33′ of the locking elastic tab 33 is fitted to the hole 23′of the fastening section 23 as shown in FIGS. 3A and 3C. Accordingly,the closed state of the disk cartridge 1 is maintained. On the otherhand, as shown in FIGS. 3B and 3D, when the disk cartridge 1 is opened,the locking elastic tab 33 is pressed in the direction of the arrow AR3.Accordingly, the elastic tab 33 is elastically deformed about thesupport point of the base portion, and the projection 33′ is disengagedfrom the hole 23′ of the fastening section 23. Accordingly, the uppercase 2 and the lower case 3 are released from the engagement. Theprojection 33′ and the fastening section 23 are machined to have taperedconfigurations so that the portions, which firstly make the contact witheach other, are spread toward the outer surfaces of the casesrespectively. Accordingly, when the disk cartridge 1 is closed, theprojection 33′ slides on the inner wall of the fastening section 23,making it easy to fit the projection 33′ to the hole 23′. Once theprojection 33′ is fitted to the hole 23′, the projection 33′ cannot bedisengaged from the hole 23′ unless the elastic tab 33 is urged as shownin FIG. 3B. In this state, the upper arm and the lower arm are locked toone another.

Accommodation/Removal of Disk in/from Disk Cartridge

Next, an explanation will be made with reference to FIGS. 4A–4B and5A–5C about the accommodation and the removal of the disk 5 in/from thedisk cartridge 1. FIG. 4A shows a situation to accommodate the disk 5 ina state in which the upper case 2 and the lower case 3 of the diskcartridge 1 are open. The disk 5 having a stack-ring 57 which defines anunrecordable area 55 is placed on the lower case 3 (arrow AR4) while theouter circumferential edge of the disk 5 is guided by the bridge 31which is formed on the lower case 3 and inner wall portions of ribs 39on which the locking elastic tabs 33 and other components are formed.Subsequently, the upper case 2 is overlapped on the lower case 3 whilerotating the upper case 2 in the direction of the arrow AR4′ about therotary shaft of the hinge 7. As described above, when the projections33′ of the locking elastic tabs 33 of the lower case 3 are engaged withthe holes 23′ of the fastening sections 23 of the upper case 2, the diskcartridge 1 is in the closed state. Accordingly, as shown in FIG. 4B,the disk 5 is accommodated in the disk cartridge 1. In the closed state,the stack-ring 57 is exposed through the openings 20 and 30, since theopenings 20 and 30 have the semicircular portions each of which has alarger diameter than that of the stack-ring 57 (as shown in FIG. 1A).

When the disk 5 is removed from the cartridge 1, the locking elastictabs 33 of the disk cartridge 1 in which the disk 5 is accommodated arepressed in the direction of the arrow AR5 as the inward direction of thedisk cartridge 1 as shown in FIG. 5A. Accordingly, the projections 33′of the lower case 3, which have been engaged with the fastening sections23 of the upper case 2 as described above, are moved in the directiontoward the center of the disk cartridge. The projections 33′ aredisengaged from the holes 23′ of the fastening sections 23, and theupper case 2 and the lower case 3 are released from the engagement.Subsequently, the upper case 2 is rotated about a base point of thehinge 7 to disengage it from the lower case 3 so that the disk cartridge1 is open. In this state, the disk 5, which has been accommodated in thedisk cartridge 1, can be removed with ease.

Insertion of Disk Cartridge into Information-Recording/ReproducingApparatus

Next, an explanation will be made with reference to FIG. 6 about theinsertion of the disk cartridge 1 into theinformation-recording/reproducing apparatus. The direction, in which thedisk cartridge 1 is inserted, can be changed in conformity with theinformation-recording/reproducing apparatus to be used. As shown in FIG.6, the flat sections 61, which are parallel to the central plane AX, areformed on the outer circumference of the disk cartridge 1. When the diskcartridge 1 is inserted into the unillustratedinformation-recording/reproducing apparatus from the side on which thebridges 21, 31 are formed (in the direction of the arrow AR6), the flatsections 61 function as guides for inserting the disk cartridge 1.Accordingly, the disk cartridge 1 can be reliably inserted into theinformation-recording/reproducing apparatus. Further, the flat sections62, 63 are formed in the vicinity of the hinge 7 of the disk cartridge 1and in the vicinity of the joining portions of the bridges 21, 31respectively. The flat sections 62, 63 are formed so that they areparallel to the plane BX which is perpendicular to the plane AX andwhich passes through the center X of the disk cartridge 1. When the diskcartridge 1 is inserted into the information-recording/reproducingapparatus in the certain direction of the plane BX (in the direction ofthe arrow AR6′), the flat sections 62, 63 can be used as guides.

The disk cartridge 1 in this embodiment was formed so that the entirelength “a” of the disk cartridge in the direction along the plane AX was85.0 mm, the entire length of the disk cartridge in the direction alongthe plane BX, i.e., the width “b” between the flat sections 61 was 80.5mm, and the length “c” between the hinge 7 and the flat sections 63 inthe direction along the plane AX was 78.5 mm. The disk cartridge 1 issubstantially circular. In order to provide the fastening sections (23)and the locking elastic tabs (33) for the disk cartridge 1 as describedabove, those disposed in the vicinity of the bridge 21 and thosedisposed in the vicinity of the flat section 61 are formed to havedifferent radii of curvature. The disk cartridge 1 was formed so thatthe radius of curvature R₁ of the outer circumference of the diskcartridge at the bridge 21 and in the vicinity thereof and the radius ofcurvature R₄ of the outer circumference of the disk cartridge in thevicinity of the hinge 7 were 49.7 mm respectively, and the radii ofcurvature R₂, R₃ of the outer circumference of the disk cartridge in thevicinity of the flat sections 61 were 41.6 mm respectively. The diskcartridge 1 was formed so that the length “d” of the flat section 61 inthe direction along the plane AX was 29.5 mm, the length “e” of the flatsection 62 in the direction along the plane BX was 19.8 mm, the length“f” of the flat section 63 in the direction along the plane BX was 4.9mm, and the width “g” of the bridge 21 in the in-plane direction was 6.6mm. The flat section 61 is formed to have the length “d” which has aratio of 34.7% with respect to the length “a” of the disk cartridge 1 inthe direction along the plane AX. In this embodiment, it is preferablethat the disk cartridge is formed so that the ratio (d/a) is within arange of 30 to 40%. More preferably, the ratio is within a range of 30to 40% in order to miniaturize the disk cartridge while utilizing theflat sections 61 as the guides.

The disk cartridge 1 was formed so that the opening width “h” of theopening 30 of the disk cartridge 1 in the direction along the plane BXwas 39.2 mm. The thickness “i” of the bridge 21 (or 31) is 2.4 mm whichis formed to be thin, i.e., about a half of the thickness “j”=5.2 mm ofthe disk cartridge 1. When the bridge portion is formed to have thethickness which is thinner than the thickness of the disk cartridge, itis possible to avoid the erroneous insertion of the disk cartridge 1into the information-recording/reproducing apparatus. Specifically, theshape of the deep portion or the insertion port of theinformation-recording/reproducing apparatus for inserting the diskcartridge is structured to have such a size that only the thickness ofthe bridge 21 (or 31) is receivable. Accordingly, even if it is intendedto insert the disk cartridge 1 reversely front to back or left to right,then it is impossible to install the disk cartridge at the finalinstallation position, or it is impossible to insert the disk cartridgeitself into the insertion port. Thus, it is possible to reliably avoidthe erroneous insertion. Considering the purpose to avoid the erroneousinsertion as described above and the mechanical strength of the bridge,it is preferable that the thickness of the bridge is adjusted to be 30to 60% with respect to the maximum thickness of the disk cartridge 1.When the disk cartridge 1 of this embodiment is inserted into theunillustrated information-recording/reproducing apparatus, the recordingand reproducing head of the information-recording/reproducing apparatusis inserted from the side of the bridge 21 (or 31).

As shown in FIG. 6, slotted hole-shaped alignment holes 65, 65′ and aperfect circular location hole 67 may be provided on the surface of thedisk cartridge 1 in the vicinity of the outer circumference. Thealignment hole 65 is formed so that the long axis is arranged in thedirection of the plane AX. The alignment hole 65′ is formed so that thelong axis is arranged in the direction of the plane BX. The alignmentholes 65, 65′ and the location hole 67 are provided in order to positionthe disk cartridge 1 in the information-recording/reproducing apparatuswhen the disk cartridge 1 is inserted into theinformation-recording/reproducing apparatus. When the disk cartridge 1is inserted into the information-recording/reproducing apparatus,reference pins, which are provided on theinformation-recording/producing apparatus and which correspond to thealignment holes 65, 65′ and the location hole 67 respectively, arefitted to the alignment holes 65, 65′ and the location hole 67.Accordingly, the disk cartridge 1 is positioned.

In the embodiment described above, the shape of the disk cartridge issubstantially circular. However, it is enough that a part of the contourof the disk cartridge has a curved portion formed substantially alongthe outer circumferential shape of the disk. For example, a part of thecontour of the disk cartridge may be sector-shaped or semicircular.

In the embodiment described above, the upper case 2 and the lower case3, which are formed separately, are connected to one another by the aidof the hinge 7. However, a hinge section may be previously formed bymeans of the integrated formation together with the upper case and thelower case. Accordingly, the number of part is one, in which it ispossible to simplify the production steps, and it is possible to omitthe assembling steps.

In the embodiment described above, the openings are provided for both ofthe upper case 2 and the lower case 3. However, in the case of a mediumon which information is recorded and reproduced only from one surfaceside of the disk, the opening may be provided on only any one of thesurfaces of the upper case 2 and the lower case 3.

In the embodiment described above, the engaging sections for engagingthe upper case 2 and the lower case 3 are provided in the vicinity ofthe bridge at the positions opposed to the hinge. However, the positionof the engaging section is arbitrary provided that the engaging sectionis not released from the engagement with ease. The mechanism of theengaging section is not limited to the arm type structure as describedabove, and it is possible to adopt various forms including, for example,a pin and a hole. The number of engaging section or engaging sections isnot limited to two. The number may be one, or two or more, for example,three or four. When the number of engaging section is one, for example,an engaging section may be provided for the bridge, or a rotary shaftmay be provided in the vicinity of the both ends of the bridge, and anengaging section may be provided on a side opposite to the bridge.

The disk cartridge of the present invention is formed to besubstantially circular, and it has the simple structure having neithershutter nor disk holder. Therefore, the disk cartridge of the presentinvention is compact, and the number of parts is small. It is possibleto simplify the production steps, and it is possible to lower theproduction cost. Further, it is easy to accommodate the disk in the diskcartridge. Therefore, it is possible to eliminate any danger concerningthe handling inconvenience.

The disk cartridge of the present invention is assembled by the hingeand the engaging sections disposed at the two positions. The cartridgeis suppressed for the opening which would be otherwise caused by anyexternal impact. Further, the cartridge of the present invention is thethin plate formed product composed of synthetic resin such aspolycarbonate. Therefore, it is possible to avoid the deformationincluding, for example, warpage and floating of the end surface.

1. A disk cartridge which accommodates an information-recording disk,the disk cartridge comprising: an upper case which has a first engagingsection; a lower case which has a second engaging section engageablewith the first engaging section and which defines a disk-accommodatingsection when the lower case overlaps with the upper case; and a movablesection which is provided for the upper case and/or the lower case andwhich rotates the upper case relative to the lower case, wherein: eachof the upper case and the lower case is formed to be substantiallycircular while having at least a pair of parallel flat sections disposedat opposing positions on an outer circumference, the parallel flatsections each having a second opening formed therein; and a firstopening is provided on at least one of surfaces of the upper case andthe lower case.
 2. The disk cartridge according to claim 1, wherein thefirst opening is open so that an information-recording surface and acentral portion of the information-recording disk are exposed.
 3. Thedisk cartridge according to claim 1, further comprising a bridge whichis provided at an end of each of the upper case and the lower case on aside on which the first opening is formed.
 4. The disk cartridgeaccording to claim 3, wherein the bridge is formed to have a thicknesswhich is thinner than a thickness of the disk cartridge.
 5. The diskcartridge according to claim 1, wherein the upper case, the lower case,and the movable section are formed by integrated formation.
 6. The diskcartridge according to claim 1, further comprising theinformation-recording disk accommodated in the disk cartridge.
 7. A diskcartridge which accommodates an information-recording disk and which isinserted into an information-recording/reproducing apparatus to recordand/or reproduce information, the disk cartridge comprising: an uppercase and a lower case each of which has a first opening for inserting aspindle and a head of the information-recording/reproducing apparatus,the first opening being formed over a region ranging from a centralportion of the disk cartridge to an end of the disk cartridge, wherein:the upper case and the lower case are openable/closable by a hinge withengaging sections for maintaining a closed state being provided at leastat two positions on a side opposite to the hinge as viewed from a centerof the disk cartridge; and end portions which are defined by the firstopening and which are disposed at an end of the disk cartridge areconnected by a bridge.
 8. The disk cartridge according to claim 7,further comprising the information-recording disk accommodated in thedisk cartridge.
 9. The disk cartridge according to claim 7, wherein eachof the upper case and the lower case is formed to be substantiallycircular while having at least a pair of parallel flat sections disposedat opposing positions on an outer circumference, the parallel flatsections each having a second opening formed therein.